JP4043294B2 - LCD projector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal projector that magnifies and projects an image of a liquid crystal panel, and more particularly to an improvement in the structure of a polarization conversion element.
[0002]
[Prior art]
The liquid crystal projector has a function of enlarging and projecting an image of the liquid crystal panel using a lamp light source. With regard to this liquid crystal projector, along with the progress of liquid crystal panels, lamps and optical technology, recently a high-brightness type that can enjoy a large screen even in a bright room has appeared, but on the other hand, due to an increase in the amount of light for each optical element Thermal load is increasing. When the thermal load is increased in this way, the liquid crystal panel, the incident / exit polarizing plate, the retardation film of the polarization conversion element and the adhesive to be adhered are made of an organic substance, and there is a problem in the optical system because it is particularly vulnerable to the thermal load. So cooling is required.
[0003]
Therefore, regarding liquid crystal panels and input / output polarizing plates, JP-A-11-231277, JP-A-2001-75070, and JP-A-9-113906 increase the cooling efficiency by using a heat transfer transparent substrate having high thermal conductivity. Proposing technology. However, these do not correspond to the polarization conversion element cooling for improving the light use efficiency.
[0004]
In high-brightness projectors, polarization conversion elements that illuminate random light from lamps with the same polarization axis are used to improve the light utilization efficiency. In the polarization conversion element 4B as shown in FIG. 4, a retardation film 44 and an adhesive for attaching the retardation film are generally used, but the retardation film 44 is heated to a high temperature of 80 to 100 ° C. If it becomes, there exists a problem that the characteristic of a film deteriorates. For this reason, it is necessary to suppress the temperature rise by forced air cooling with a fan.
[0005]
[Problems to be solved by the invention]
However, since the power of the lamp has increased with the recent trend of increasing the brightness and downsizing of liquid crystal projectors, the concentration of luminous flux due to the downsizing of the polarization conversion element 4B has increased the temperature by forced air cooling with a fan. There is a limit to suppression. If the temperature increase cannot be suppressed within the temperature specification, the retardation film 44 may be discolored, burnt, or the temperature of the incident polarizing plate may increase due to a decrease in the polarization conversion element. Overall reliability will be reduced. Further, when the number of rotations of the fan is increased in order to enhance the cooling effect, the motor sound and wind noise of the fan increase accordingly, resulting in an increase in the noise value of the entire product, resulting in deterioration of the quality.
[0006]
In order to solve these problems, Japanese Patent Laid-Open No. 2001-318359 proposes a technique for forming the polarization conversion element 4B using sapphire glass having high heat dissipation. Japanese Patent Application Laid-Open No. 2001-6281 proposes a technique in which a heat transfer transparent base material such as sapphire glass is disposed as a heat dissipation means on the exit side of the retardation film 44 of the polarization conversion element 4B.
[0007]
However, in the case of the technique disclosed in Japanese Patent Application Laid-Open No. 2001-318359, when the entire polarization conversion element 4B is made of sapphire glass, the dielectric film 42 and the total reflection film 43 that allow the sapphire glass to transmit P-wave light and reflect S-wave light. Must be laminated. In addition, there is a problem that the total cost increases due to cutting and polishing of the hard sapphire glass, which hinders commercialization.
[0008]
In addition, since the entire polarization conversion element 4B is made of sapphire glass made of the same base material, an optical path difference between the transmitted P wave and the reflected S wave by the polarization conversion element 4B is inevitably generated, and the imaging light beam to the liquid crystal panel is generated. Deviation occurs. At present, in order to minimize the deviation, it is common to optically design the condenser lens so as to average the optical path difference between the transmitted P wave and the reflected S wave.
However, fundamentally, since the misalignment of the liquid crystal panel image formation due to the optical path difference between the P wave and the S wave by the polarization conversion element 4B remains, as a result, the screen quality such as color unevenness is lowered.
[0009]
Furthermore, in the case of the technique disclosed in Japanese Patent Application Laid-Open No. 2001-6281, since a heat transfer transparent base material such as sapphire glass must be additionally arranged, there is a problem that transmission loss occurs, resulting in a decrease in screen brightness. is there.
[0010]
The present invention has been made in view of the above, and can contribute to commercialization by suppressing an increase in the total cost, and it is possible to reduce the screen quality such as occurrence of misalignment of imaging light rays and color unevenness with respect to the liquid crystal panel. An object of the present invention is to provide a liquid crystal projector capable of preventing the suppression and preventing the screen brightness from being lowered.
[0011]
[Means for Solving the Problems]
In the present invention, in order to solve the above-described problem, the light source generates white light, the first lens array including a plurality of rectangular lenses, and the plurality of rectangular lenses corresponding to the lens cells of the first lens array. a second lens array, a polarization conversion element for aligning the polarization direction of the light from the light source into one, and a liquid crystal panel for modulating polarized light in one direction emitted from the polarization conversion element, a liquid crystal panel modulated light A projection lens for projecting by:
The polarization conversion element is configured by alternately arranging two types of transparent substrates having different thermal conductivities, and the transparent substrate having a higher thermal conductivity has a thermal conductivity of 40 to 45 W / (m · K). ) Sapphire glass or quartz glass having a thermal conductivity of 5 to 10 W / (m · K ), and only the transparent substrate portion having the higher thermal conductivity among the light exit surfaces of the polarization conversion elements. A phase difference film,
Of the two sides facing the transparent base material having the higher the thermal conductivity of the thermal conductivity is lower transparent substrate, on one side causes transmits the P-wave of light, reflecting the S-wave A dielectric film to be laminated is laminated, and a total reflection film or a dielectric film is laminated on the other side .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. A liquid crystal projector according to the present embodiment includes a white light source 1 for generating white light and a plurality of rectangular lenses as shown in FIGS. The first lens array 2, the second lens array 3 composed of a plurality of rectangular lenses corresponding to the lens cells of the first lens array 2, and the polarization direction of the light from the white light source 1 are aligned. A polarization conversion element 4, a liquid crystal panel 7 that modulates polarized light in one direction emitted from the polarization conversion element 4, and a projection lens 10 that projects the modulated light by the liquid crystal panel 7 are provided.
[0015]
In the figure, reference numeral 1 denotes a white light source. The white light source 1 includes a first lens array 2 having a plurality of lenses for uniformly illuminating the liquid crystal panel 7, and each lens cell of the first lens array 2. A second lens array 3 composed of a plurality of rectangular lenses that form an arc image of the light source as a secondary light source image with the number of cells corresponding to the number of cells, and the polarization direction of the light for improving the light utilization efficiency from the white light source 1 A single polarization conversion element 4 is arranged. The second lens array 3 and the first and second condenser lenses 5 and 6 are optically designed and arranged so that each cell on the first lens array 2 forms an image on the liquid crystal panel 7.
[0016]
The light transmitted through the first and second condenser lenses 5 and 6 is separated into red, green, and blue by a plurality of dichroic mirror units 8 and enters each liquid crystal panel 7. The light transmitted through each liquid crystal panel 7 is color-combined by the cross prism 9 and enlarged and projected onto the screen 11 by the projection lens 10.
[0017]
Next, an enlarged view of the second lens array 3 and the polarization conversion element 4 is shown in FIG. The polarization conversion element 4 in the figure is configured by alternately arranging two different types of transparent base materials 40 and 41. Random light (PS wave) transmitted through the second lens array 3 is transmitted through the dielectric film 42 by the P wave, reflected by the S wave, and reflected by the total reflection film 43 in the same direction as the P wave.
Although the total reflection film 43 is shown in the present embodiment, a dielectric film 42 may be used in place of the total reflection film 43 (hereinafter the same).
[0018]
The reflected S wave is rotated to a P wave by the phase difference film 44 and exits the polarization conversion element 4 as the same polarized light as the P wave.
In FIG. 2, the case where the polarization conversion element 4 is emitted as a P wave will be described. However, when the polarization conversion element 4 is emitted as an S wave, the P wave transmitted through the dielectric film 42 is transmitted by the retardation film 44. The S wave that is rotated and reflected by the dielectric film 42 is reflected by the total reflection film 43 and exits the polarization conversion element 4 with the S wave remaining unchanged.
[0019]
Here, in order to suppress the temperature rise of the retardation film 44, sapphire glass having a thermal conductivity of 40 to 45 W / Mk or a thermal conductivity of 5 to 5 is provided on the transparent base material 40 side to which the retardation film 44 is adhered. A 10 W / Mk quartz glass is used. With such a configuration, the cooling efficiency of the polarization conversion element 4 is improved and the performance deterioration of the retardation film 44 is reduced, so that the product life can be extended, and a liquid crystal projector with low fan noise can be achieved. Obtainable.
[0020]
In addition, in order to improve cost merit, a dielectric film 42 is laminated on one side of the transparent substrate 41 that is not sapphire glass or quartz glass and has low thermal conductivity, and total reflection is performed on the other side of the transparent substrate 41. The film 43 or the dielectric film 42 is laminated. Compared to the case of JP 2001-318359 A, in which the sapphire glass is used as the whole of the polarization conversion element 4 by making this structure and costly sapphire glass or quartz glass about half of the polarization conversion element 4, Total cost can be significantly reduced.
[0021]
In the case of Japanese Patent Application Laid-Open No. 2001-318359, since the entire polarization conversion element 4 is sapphire glass, an optical path difference between a transmitted P wave and a reflected S wave by the polarization conversion element 4 inevitably occurs. Deviation of the imaging light beam with respect to 7 occurred.
On the other hand, according to the present embodiment, the polarization conversion element 4 is composed of two different types of transparent base materials 40 and 41, so that the difference in refractive index between the transparent base materials 40 and 41 is increased by the polarization conversion element 4. It is possible to reduce the optical path difference between the wave and the S wave. Further, the subsequent optical design of the condenser lens can be carried out without difficulty, and the image formation of the liquid crystal panel 7 becomes good, resulting in a significant improvement in screen quality such as color unevenness.
[0022]
Hereinafter, this will be described as a second embodiment with reference to FIG. The polarization conversion element 4A in the figure is configured by alternately arranging transparent substrates 40A and 41A having two different types of refractive indexes. Random light (PS wave) that has passed through the second lens array 3 is transmitted through the P wave by the dielectric film 42, reflected by the S wave, and reflected by the total reflection film 43 in the same direction as the P wave. The reflected S wave is rotated to a P wave by the phase difference film 44, and exits the polarization conversion element 4A as the same polarized light as the P wave.
Note that FIG. 3 illustrates the case where the polarization conversion element 4A is emitted as a P wave, but when the polarization conversion element 4A is emitted as an S wave, the P wave transmitted through the dielectric film 42 is transmitted by the phase difference film 44. The S wave that has been rotated and reflected by the dielectric film 42 is reflected by the total reflection film 43 and is emitted from the polarization conversion element 4A as the S wave.
[0023]
Here, among the two types of transparent base materials 40A and 41A constituting the polarization conversion element 4A, the refractive index of one type of transparent base material 40A having a high refractive index is n2, and other types of transparent base materials having a low refractive index. When the refractive index of 41A is n1, the relationship of n1 <n2 is established, and if the pitch of the transparent substrates 40A and 41A that are alternately positioned is d, the optical path length difference between P1 and P2 in FIG. It becomes like this.
((3 / n2) − (1 / n1)) × d / 2 Formula (1)
[0024]
Next, FIG. 4 shows a conventional polarization conversion element 4B using a single transparent substrate 40B. When the refractive index of the transparent substrate 40B is n1, the optical path length difference between P1 ′ and P2 ′ is as follows.
d / n1 Formula (2)
[0025]
Subtracting equation (1) from equation (2) yields:
((1 / n1) − (1 / n2)) × 3 × d / 2 Equation (3)
Due to the relationship of n1 <n2,
((1 / n1) − (1 / n2)) × 3 × d / 2> 0 Equation (4)
Always positive, indicating that the optical path length difference of the present invention is small.
[0026]
Hereinafter, when using a specific example, when the transparent substrate 40A / 41A pitch d is 3.5 mm, the transparent substrate 40A is sapphire glass, and the transparent substrate 41B is BK7 glass, The refractive index n2 of the material 40A is 1.8 and the refractive index n1 of the transparent base material 41A is 1.5, and the optical path length difference between P1 ′ and P2 ′ is about 1.75 mm according to the equation (1).
On the other hand, in the case of the conventional uniform transparent substrate 40B using general BK7 glass, the optical path length difference between P1 ′ and P2 ′ is about 2.33 mm according to the equation (2).
[0027]
According to the present embodiment, it is possible to reduce the optical path length difference of about 25% P wave and S wave compared to the conventional comparative example. Thereby, each optical path length difference separated into the P wave and the S wave becomes small, and the subsequent optical design of the condenser lens can be carried out without difficulty. Further, the deviation of the imaged light beam with respect to the liquid crystal panel 7 due to the polarization conversion is reduced, the image formation is superposed well, and the improvement of the screen quality can be greatly expected.
[0028]
【The invention's effect】
As described above, according to the present invention, the light source that generates white light, the first lens array including the plurality of rectangular lenses, and the first lens array including the plurality of rectangular lenses corresponding to the lens cells of the first lens array. a second lens array, a polarization conversion element to align in a single polarization direction of the light from the light source, and a liquid crystal panel for modulating polarized light in one direction emitted from the polarization conversion element, by the modulated light liquid crystal panel A projection lens for projection, and the polarization conversion element is configured by alternately arranging two types of transparent substrates having different thermal conductivities , and the thermal conductivity of the transparent substrate having the higher thermal conductivity is determined. 40~45W / (m · K) sapphire glass or the thermal conductivity of the quartz glass of 5~10W / (m · K), of the light emitting surface of the polarization conversion element, the thermal conductivity higher place only in a portion of the transparent base material The difference film provided, among the two sides facing the transparent base material having the higher the thermal conductivity of the thermal conductivity is lower transparent substrate, on one side causes transmits P wave light Since a dielectric film that reflects S-wave is laminated and a total reflection film or dielectric film is laminated on the other side, it is possible to contribute to commercialization by suppressing an increase in total cost. It is possible to prevent and suppress the deterioration of the screen quality such as the occurrence of misalignment of the imaging light beam and the color unevenness with respect to the panel, and the reduction of the screen brightness.
[0029]
Specifically, since the cooling efficiency is improved and the performance deterioration of the retardation film can be reduced, the product life can be extended and a projector with low fan noise can be obtained. In addition, since expensive sapphire glass and quartz glass are partially used at necessary places instead of all, it is possible to suppress and prevent an increase in cost. Furthermore, the transparent substrate having two different refractive indexes is alternately arranged to form a polarization conversion element, and the optical path length is corrected by the difference in refractive index between the two types of transparent substrates, so that the image forming beam for the liquid crystal panel Is reduced, the image formation is superposed, and the quality of the screen is improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an optical system arrangement in an embodiment of a liquid crystal projector according to the present invention.
FIG. 2 is a configuration diagram showing a polarization conversion element and the like in an embodiment of a liquid crystal projector according to the present invention.
FIG. 3 is a configuration diagram showing a polarization conversion element and the like in a second embodiment of a liquid crystal projector according to the present invention.
FIG. 4 is a configuration diagram showing a polarization conversion element and the like in a conventional liquid crystal projector.
[Explanation of symbols]
1 White light source (light source)
2 First lens array 3 Second lens array 4 Polarization conversion element 4A Polarization conversion element 7 Liquid crystal panel 10 Projection lens 40 Transparent substrate 40A Transparent substrate 41 Transparent substrate 41A Transparent substrate 42 Dielectric film (film)
43 Total reflection film
44 retardation film

Claims (1)

A light source that generates white light, a first lens array that includes a plurality of rectangular lenses, a second lens array that includes a plurality of rectangular lenses corresponding to each lens cell of the first lens array, and light from the light source of a polarization conversion element for aligning the polarization direction into one liquid crystal and a liquid crystal panel for modulating polarized light in one direction emitted from the polarization conversion element, the modulated light comprising a projection lens for projecting the liquid crystal panel A projector,
The polarization conversion element is configured by alternately arranging two types of transparent substrates having different thermal conductivities, and the transparent substrate having a higher thermal conductivity has a thermal conductivity of 40 to 45 W / (m · K). ) Sapphire glass or quartz glass having a thermal conductivity of 5 to 10 W / (m · K ), and only the transparent substrate portion having the higher thermal conductivity among the light exit surfaces of the polarization conversion elements. A phase difference film,
Of the two sides facing the transparent base material having the higher the thermal conductivity of the thermal conductivity is lower transparent substrate, on one side causes transmits the P-wave of light, reflecting the S-wave A liquid crystal projector, wherein a dielectric film to be laminated is laminated, and a total reflection film or a dielectric film is laminated on the other side .

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